Veins are thin-walled and contain one-way valves that control blood flow. Normally, the valves open to allow blood to flow into the deeper veins and close to prevent back-flow into the superficial veins. When the valves are malfunctioning or only partially functioning, however, they no longer prevent the back-flow of blood into the superficial veins. As a result, venous pressure builds at the site of the faulty valves. Because the veins are thin walled and not able to withstand the increased pressure, they become what are known as varicose veins which are veins that are dilated, tortuous or engorged.
In particular, varicose veins of the lower extremities is one of the most common medical conditions of the adult population. It is estimated that varicose veins affect approximately 25% of adult females and 10% of males. Symptoms include discomfort, aching of the legs, itching, cosmetic deformities, and swelling. If left untreated, varicose veins may cause medical complications such as bleeding, phlebitis, ulcerations, thrombi and lipodermatosclerosis.
Traditional treatments for varicosities include both temporary and permanent techniques. Temporary treatments involve use of compression stockings and elevation of the diseased extremities. While providing temporary relief of symptoms, these techniques do not correct the underlying cause, that is the faulty valves. Permanent treatments include surgical excision of the diseased segments, ambulatory phlebectomy, and occlusion of the vein through chemical or thermal means.
Surgical excision requires general anesthesia and a long recovery period. Even with its high clinical success rate, surgical excision is rapidly becoming an outmoded technique due to the high costs of treatment and complication risks from surgery. Ambulatory phlebectomy involves avulsion of the varicose vein segment using multiple stab incisions through the skin. The procedure is done on an outpatient basis, but is still relatively expensive due to the length of time required to perform the procedure.
Chemical occlusion, also known as sclerotherapy, is an in-office procedure involving the injection of an irritant chemical into the vein. The chemical acts upon the inner lining of the vein walls causing them to occlude and block blood flow. Although a popular treatment option, complications can be severe including skin ulceration, anaphylactic reactions and permanent skin staining. Treatment is limited to veins of a particular size range. In addition, there is a relatively high recurrence rate due to vessel recanalization.
Endovascular laser therapy is a relatively new treatment technique for venous reflux diseases. In that technique, the laser energy is delivered by a flexible optical fiber that is percutaneously inserted into the diseased vein prior to energy delivery. An introducer catheter or sheath is first inserted and advanced to within a few centimeters of the saphenous-femoral junction of the greater saphenous vein. Once the introducer catheter is properly positioned, a flexible optical fiber is inserted into the lumen of the catheter or sheath and advanced until the fiber tip is near the catheter tip but still protected within the catheter lumen.
For proper positioning, a medical tape is conventionally used to pre-measure and mark the optical fiber before insertion into the catheter. The physician measures the catheter length and then marks the fiber with the tape at a point approximately 1–3 centimeters longer than the overall catheter length. This measurement is used to establish correct placement of the fiber tip relative to the catheter in an exposed position.
Prior to laser activation, the catheter is withdrawn approximately 1–3 centimeters (position being indicated by a tape mark or the like) to expose the distal tip of the optical fiber. The laser generator is then activated causing laser energy to be emitted from the bare flat tip of the fiber into the vessel. The energy contacts the blood causing hot bubbles of gas to be created. The gas bubbles transfer thermal energy to the vein wall, causing cell necrosis and eventual vein collapse. With the laser generator turned on, the fiber and catheter are slowly withdrawn as a single unit until the entire diseased segment of the vessel has been treated.
For such endovascular laser treatment, the position of the fiber tip relative to the catheter is considered to be a very important parameter. Current laser treatment protocols recommend exposing the fiber tip by holding the fiber element stationary while withdrawing the catheter approximately 1 to 3 centimeters. Location of the fiber tip is then confirmed using ultrasound guidance and direct visualization of the red aiming beam of the fiber. Once correct positioning has been verified, the optical fiber is secured to the introducer catheter, typically with medical grade adhesive tape to ensure that the fiber and the catheter do not move independently of each other during the laser procedure.
As can be appreciated, there are many problems associated with using a medical tape for fiber positioning prior to insertion into the catheter or for joining the fiber and catheter together. It is cumbersome, inaccurate and time-consuming for the treating physician. Moreover, using the tape for positioning may cause damage to the fiber as the physician must straighten out the fiber for measurement. The tape may also be incorrectly located on the fiber. When using the tape to join the fiber and catheter together, it is possible that the tape does not adequately hold them in a stationary position, resulting in improper alignment of the fiber with respect to the catheter.
Complications caused by mishandling and improper positioning of the optical fiber can be severe. Mishandling can result in fiber breakage or incomplete energy delivery. Improper positioning of the fiber relative to the catheter cause other problems. If the fiber tip is too close to the catheter tip, the catheter material may be thermally heated by the laser energy to the extent that the catheter tip integrity is compromised. If the fiber tip extends too far from the catheter tip, the exposed portion of the fiber tip may become damaged or cause energy to be delivered to a non-target area during withdrawal. For example, the physician may begin laser treatment at a point in the venous system that is too deep, resulting in possible deep vein thrombosis. Improper positioning of the tip may also cause the physician to stop treatment prematurely resulting in a non-occluded vessel segment.
Therefore, it is desirable to provide a reliable endovascular laser treatment device that safely stops the optical fiber in a protective position during insertion and safely secures the fiber in an operating position without using a medical tape and without requiring the user to pre-measure the optical fiber.
It is also desirable to provide such an endovascular laser treatment device that can be manufactured at a low cost and that can reduce the fiber insertion time.